Most surfactants presently used in detergent and personal product compositions are based on, or derived largely from, petrochemicals. Because of increased concern over environmental issues raised by the use, handling and storage of such materials as well as the continually rising costs of such materials, it would be advantageous to develop surfactants which are instead derived from agriculturally grown substances such as carbohydrates. These naturally occurring compounds represent a source of renewable raw materials which are synthetically versatile, inexpensive, aquatically favorable, optically pure and environmentally friendly. In addition, it is most desirable to have surfactants that provide an enhanced copious persistent foam while simultaneously providing an enhanced solubility in water and in aqueous detergent, personal product and oral hygiene compositions. This has become a difficult challenge to meet and it is not surprising to find that considerable resource and effort have been directed towards the discovery and development of new surfactants that provide improved foam and solubility characteristics. The patent literature, cosmetic journals and formularies describe many such compounds, however, they still do not provide all the answers to the problems encountered in making a totally satisfactory surfactant, particularly alkyl aldonamide surfactants. For one thing, it is known that prior art alkyl aldonamides exhibit poor water solubility and little or no foaming performance. While not wishing to be bound by theory, it is believed that the amphiphilic nature of these compounds cause them to pack closely in the solid state through strong amide/hydroxyl hydrogen bonding as well as strong hydrocarbon Van der Waal forces. The net result is an unfavorable heat of hydration, a high Krafft point, low water solubility (precipitation), a poor rate of micellization, an unfavorable surface tension and a poor foaming profile.
It has now been found that the inclusion of a heteroatom in the alkyl chain of an aldonamide compound produces a nonionic surfactant that surprising exhibits a superior water solubility and foaming performance. While not wishing to be bound by theory, it is believed that heteroatom containing alkyl aldonamide compounds pack more loosely (favorably) in the solid state through weaker amide/hydroxyl hydrogen bonding and weaker hydrocarbon Van der Waal forces. The net result is a more favorable heat of hydration, a lower Krafft point, an increased water solubility, an enhanced rate of micellization, a low surface tension and a superior foaming profile.
In addition, it has also been found that the heteroatom containing alkyl aldonamide compounds of the present invention represent a novel, naturally derived, cost-effective, biodegradable, class of nonionic surfactant which have surfactant properties equal to, or better than, other well known petrochemically derived surfactants, thereby indicating that they are viable, environmentally sound alternatives to traditional petrochemical surfactants.
These findings are quite unexpected and have not been recognized or appreciated in the art.
An aldonamide is most generally defined as the amide of an aldonic acid (or aldonolactone) and an aldonic acid, ill turn is defined as a sugar substance in which the pseudoaldehyde or pseudoketose group, generally found at the C.sub.1 or C.sub.2 position on the sugar, has been oxidized to a carboxylic acid group which upon drying cyclizes to an aldonolactone.
Aldonamides may be based on compounds comprising one saccharide unit (e.g., glyceramides, ribonamides, gluconamides or glucoheptonamides), two saccharide units (e.g., lactobionamides, maltobionamides, melibionamides, cellobioamides, gentiobionamides or D-glucopyranosyl-(1-5)-D-arabinonamides) or they may be based on compounds comprising more than two saccharide units (e.g. maltotrionamides or maltohexonamides). Any carbohydrate can be used as long as the sugar has a pseudoaldehyde or pseudoketose group available for oxidation to a carboxylic acid group.
While certain alkyl aldonamides are known in the art, there is no teaching or suggestion of the heteroatom containing alkyl aldonamide compounds of the present invention. In particular, there is no teaching or suggestion of monosaccharide heteroatom containing alkyl aldonamide compounds comprising at least two heteroatoms in the alkyl chain selected from the group consisting of amine (NH), amine salt (NHA+), ether (O), ester (COO or OOC), amide (NACO, CONA or NCOA) or mixtures thereof; and disaccharide heteroatom containing alkyl aldobionamide compounds comprising at least one heteroatom in the alkyl chain selected from the group consisting of amine (NH), amine salt (NHA+), ether (O), amide (NACO, CONA or NCOA) or mixtures thereof, wherein A is hydrogen (H) or a C.sub.1 -C.sub.18 alkyl group that may optionally contain a hydroxyl group.
More specifically, there is no teaching or suggestion of a certain novel class of heteroatom containing alkyl aldonamide compound which has improved foam, enhanced water solubility, lower surface tension and favorable critical micelle concentration relative to prior art alkyl aldonamides.
In addition, there is no teaching or suggestion of a new and improved method of manufacture of certain novel heteroatom containing alkyl aldonamide compounds, specifically alkylamidoallcyl aldonamides.